Researchers at Tohoku University in Japan have found a new way to successfully detect the efficiency of crystal semiconductors. For the first time, the team used a specific kind of photoluminescence spectroscopy, a way to detect light, to characterize the semiconductors. The emitted light energy was used as an indicator of the crystal's quality. This method will potentially yield more efficient light-emitting diodes (LEDs), solar cells and several other advances in electronics.

Internal quantum efficiency of semiconducting crystals quantified by new method imageSchematic of the ARPL measurement technique

"For further development of perovskite-based devices, it is essential to quantitatively evaluate the absolute efficiency in high-quality perovskite crystals without assuming any predefined physical model is of particular importance," said corresponding author Kazunobu Kojima, Associate Professor at Tohoku University, Japan. "Our method is new and unique because previous methods have relied on efficiency estimation by model-dependent analyses of photoluminescence."

Understanding photoluminescence is important for designing devices that control, generate or detect light, including solar cells, LEDs and light sensors. So far, detection has largely relied on theoretical modelling as a way to predict the efficiency of perovskite-based semiconductors. In this research, the authors have implemented a technique they originally proposed in 2016 called Omnidirectional Photoluminescence Spectroscopy or "ODPL spectroscopy." The procedure is a contactless, nondestructive method of probing the electronic structure of the crystals from all directions, enabling them to easily and quickly quantify the crystals' properties.

An important next step is to implement ODPL spectroscopy to investigate different types of perovskite materials. This may lead to better understanding of crystal-based semiconductors as well as more efficient ones. The authors state that their future studies will focus on both increasing crystal efficiency and ensuring that it is unified across all areas of materials.

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